Dealing with Risks

What are the safety standards that must be fulfilled by dikes, and how are these standards calculated? After the North Sea Flood of 1953, the first Delta Committee advised that flood defences for central Holland must be equipped to deal with the kind of flood that was to be expected once every 10,000 years. The calculation of this safety norm incorporated a cost-benefit analysis of the costs of reinforcing the dikes and the projected financial and economic damage caused by flooding. This was essentially an initial elaboration of a risk-based approach, which takes account of the probability of the failure of flood defences and the consequences of a flood, which might be expressed as risk = probability × consequences.

Dealing with Risks

Using Technological Innovations to Reinforce Traditional Dikes

The existing dikes too must keep up with the times. But dikes can no longer be reinforced simply by raising them again and again: height increases are not only subject to spatial and physical constraints, but also to public opposition. For instance, if historic dike houses would have to be demolished in order to raise the height of a dike, it is worth considering alternatives.

Using Technological Innovations to Reinforce Traditional Dikes

Developing Multifunctional Dikes

The dikes of the future will be more robust, multifunctional and resistant to breaches. Examples include the ‘Delta Dike’ and the multifunctional dike. The former is unbreachable, whether by water flowing over it or by waves thrashing against it. The multifunctional dike and ‘super dike’ go further still: these are wide, unbreachable dikes, which are combined with other functions and even more closely integrated into the landscape. Other designs combine several parallel structures into double or triple dikes. All these are dikes that can be modified to suit their surroundings. In other words, a dike in a rural area or on the coast will be constructed differently, and have a different profile, from one in the city. A dike in an industrial area will be very different from one in a nature reserve. Multifunctional, unbreachable and adaptable: those are the keywords that will govern the dikes of the future.

Developing Multifunctional Dikes

New Uses for Dike Relics

Future thinking about dikes will not be confined to flood defences. Besides its flood defences, the Netherlands has thousands of kilometres of dike relics. Although these no longer play a role in the country’s flood defences, they do tell a story about the history of the Netherlands. Along the dike relics, which have ‘experienced’ so much, stand numerous monuments and historic buildings. But dike relics are vulnerable: some have been sold and dug up, acts that cannot be reversed. Finding the right way to protect and use dike relics with cultural value poses a challenge. One possibility would be classify monumental dike relics as ‘protected dike views’, a category equivalent to that of protected villages and townscapes, as applied in the Netherlands. This could help to preserve the historic heritage of the dike and its surroundings.

New Uses for Dike Relics

Investing in the Dike Network

To safeguard the quality of life in the cities, it is essential for the green areas near the city to be readily accessible. Dikes can play an important role in linking the city to the countryside. The cities and villages of the Netherlands are full of dikes, both relics and current flood defences. These structures also support surface and underground infrastructure and public facilities, from roads and railway lines to tunnels, parks, and car parks. It therefore makes sense to connect the dike network of the outlying countryside to that of the city, and to ensure clear routing when doing so.